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<div class="refentry">
<a name="gtk-running"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
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<h2><span class="refentrytitle">Running GTK+ Applications</span></h2>
<p>Running GTK+ Applications — 
How to run and debug your GTK+ application
</p>
</td>
<td class="gallery_image" valign="top" align="right"></td>
</tr></table></div>
<div class="refsect1">
<a name="id-1.8.4.3"></a><h2>Running and debugging GTK+ Applications</h2>
<div class="refsect2">
<a name="id-1.8.4.3.2"></a><h3>Common commandline options</h3>
<p>
All GTK+ applications support a number of standard commandline
options. These are removed from <code class="literal">argv</code> by gtk_init().
Modules may parse and remove further options. The
<a class="link" href="gtk-x11.html#x11-cmdline" title="X11-specific commandline options">X11</a> and
<a class="link" href="gtk-windows.html#win32-cmdline" title="Windows-specific commandline options">Windows</a> GDK backends parse
some additional commandline options.
</p>
<p><b><code class="systemitem">--gtk-module <em class="replaceable"><code>module</code></em></code>. </b>
A list of modules to load in addition to those specified in the
<code class="envar">GTK3_MODULES</code> environment variable and the
<code class="literal">gtk-modules</code> setting.
</p>
<p><b><code class="systemitem">--g-fatal-warnings</code>. </b>
Make GTK+ abort on all warnings. This is useful to stop on the first
warning in a debugger, if your application is printing multiple
warnings.  It's almost always best to start debugging with the first
warning that occurs.
</p>
<p><b><code class="systemitem">--gtk-debug <em class="replaceable"><code>options</code></em></code>. </b>
A list of <a class="link" href="gtk-running.html#GTK-Debug-Options" title="GTK_DEBUG">debug options</a>
to turn on in addition to those specified in the <code class="envar">GTK_DEBUG</code>
environment variable. This option is not available if GTK+ has been
configured with <code class="option">--enable-debug=no</code>.
</p>
<p><b><code class="systemitem">--gtk-no-debug <em class="replaceable"><code>options</code></em></code>. </b>
A list of <a class="link" href="gtk-running.html#GTK-Debug-Options" title="GTK_DEBUG">debug options</a>
to turn off. This option is only available if GTK+ has been configured with
<code class="option">--enable-debug=yes</code>.
</p>
<p>
The following options are really used by GDK, not by GTK+, but we
list them here for completeness nevertheless.
</p>
<p><b><code class="systemitem">--class <em class="replaceable"><code>class</code></em></code>. </b>
Sets the program class; see gdk_set_program_class().
</p>
<p><b><code class="systemitem">--name <em class="replaceable"><code>name</code></em></code>. </b>
Sets the program name.
</p>
<p><b><code class="systemitem">--gdk-debug <em class="replaceable"><code>options</code></em></code>. </b>
A list of <a class="link" href="gtk-running.html#GDK-Debug-Options" title="GDK_DEBUG">debug options</a>
to turn on in addition to those specified in the <code class="envar">GDK_DEBUG</code>
environment variable. This option is only available if GTK+ has been
configured with <code class="option">--enable-debug=yes</code>.
</p>
<p><b><code class="systemitem">--gdk-no-debug <em class="replaceable"><code>options</code></em></code>. </b>
A list of <a class="link" href="gtk-running.html#GDK-Debug-Options" title="GDK_DEBUG">debug options</a>
to turn off. This option is only available if GTK+ has been configured with
<code class="option">--enable-debug=yes</code>.
</p>
</div>
<hr>
<div class="refsect2">
<a name="id-1.8.4.3.3"></a><h3>Environment variables</h3>
<p>
GTK+ inspects a number of environment variables in addition to standard
variables like <code class="envar">LANG</code>, <code class="envar">PATH</code>, <code class="envar">HOME</code>
or <code class="envar">DISPLAY</code>; mostly to determine paths to look for certain
files. The <a class="link" href="gtk-x11.html#x11-envar" title="X11-specific environment variables">X11</a>,
<a class="link" href="gtk-windows.html#win32-envar" title="Windows-specific environment variables">Windows</a> and
<a class="link" href="gtk-broadway.html#broadway-envar" title="Broadway-specific environment variables">Broadway</a> GDK backends use some
additional environment variables.
</p>
<p><a name="GTK-Debug-Options"></a><b><code class="envar">GTK_DEBUG</code>. </b>
  This variable can be set to a list of debug options, which cause GTK to
  print out different types of debugging information. Some of these options
  are only available when GTK has been configured with <code class="option">--enable-debug=yes</code>.
  </p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term">actions</span></p></td>
<td><p>Actions and menu models</p></td>
</tr>
<tr>
<td><p><span class="term">baselines</span></p></td>
<td><p>Show baselines</p></td>
</tr>
<tr>
<td><p><span class="term">builder</span></p></td>
<td><p>GtkBuilder support</p></td>
</tr>
<tr>
<td><p><span class="term">geometry</span></p></td>
<td><p>Size allocation</p></td>
</tr>
<tr>
<td><p><span class="term">icontheme</span></p></td>
<td><p>Icon themes</p></td>
</tr>
<tr>
<td><p><span class="term">interactive</span></p></td>
<td><p>Open the <a class="link" href="gtk-running.html#interactive-debugging" title="Interactive debugging">interactive debugger</a></p></td>
</tr>
<tr>
<td><p><span class="term">keybindings</span></p></td>
<td><p>Keybindings</p></td>
</tr>
<tr>
<td><p><span class="term">misc</span></p></td>
<td><p>Miscellaneous information</p></td>
</tr>
<tr>
<td><p><span class="term">modules</span></p></td>
<td><p>Loading of modules</p></td>
</tr>
<tr>
<td><p><span class="term">no-css-cache</span></p></td>
<td><p>Bypass caching for CSS style properties</p></td>
</tr>
<tr>
<td><p><span class="term">no-pixel-cache</span></p></td>
<td><p>Disable the pixel cache</p></td>
</tr>
<tr>
<td><p><span class="term">plugsocket</span></p></td>
<td><p>Cross-process embedding</p></td>
</tr>
<tr>
<td><p><span class="term">pixel-cache</span></p></td>
<td><p>Pixel cache</p></td>
</tr>
<tr>
<td><p><span class="term">printing</span></p></td>
<td><p>Printing support</p></td>
</tr>
<tr>
<td><p><span class="term">size-request</span></p></td>
<td><p>Size requests</p></td>
</tr>
<tr>
<td><p><span class="term">text</span></p></td>
<td><p>Text widget internals</p></td>
</tr>
<tr>
<td><p><span class="term">touchscreen</span></p></td>
<td><p>Pretend the pointer is a touchscreen device</p></td>
</tr>
<tr>
<td><p><span class="term">tree</span></p></td>
<td><p>Tree widget internals</p></td>
</tr>
<tr>
<td><p><span class="term">updates</span></p></td>
<td><p>Visual feedback about window updates</p></td>
</tr>
<tr>
<td><p><span class="term">resize</span></p></td>
<td><p>Highlight resizing widgets</p></td>
</tr>
<tr>
<td><p><span class="term">layout</span></p></td>
<td><p>Show layout borders</p></td>
</tr>
</tbody>
</table></div>
<p>
  The special value <code class="literal">all</code> can be used to turn on all
  debug options. The special value <code class="literal">help</code> can be used
  to obtain a list of all supported debug options.
  </p>
<p><b><code class="envar">GTK3_MODULES</code>. </b>
    A list of modules to load. Note that GTK+ also allows to specify modules to load via a commandline option (<code class="option">--gtk-module</code>) and with the <code class="literal">gtk-modules</code> setting.
  </p>
<p><b><code class="envar">GTK_MODULES</code>. </b>
    A list of modules to load in addition to the ones in the <code class="envar">GTK3_MODULES</code> variable.
  </p>
<div class="warning">
    Note that this environment variable is read by GTK+ 2.x too,
    which may not have the same set of modules available for loading.
    Use <code class="envar">GTK3_MODULES</code> for modules that are only compatible
    with GTK+ 3.
  </div>
<p><a name="gtk-path"></a><b><code class="envar">GTK_PATH</code>. </b>
    Specifies a list of directories to search when GTK+ is looking for
    dynamically loaded objects such as the modules specified by
    <code class="envar">GTK_MODULES</code>, theme engines, input method
    modules, file system backends and print backends. If the path to
    the dynamically loaded object is given as an absolute path name,
    then GTK+ loads it directly.
    Otherwise, GTK+ goes in turn through the directories in <code class="envar">GTK_PATH</code>,
    followed by the directory <code class="filename">.gtk-3.0</code> in the user's
    home directory, followed by the system default directory,
    which is <code class="filename"><em class="replaceable"><code>libdir</code></em>/gtk-3.0/modules</code>.
    (If <code class="envar">GTK_EXE_PREFIX</code> is defined, <em class="replaceable"><code>libdir</code></em> is
    <code class="filename">$GTK_EXE_PREFIX/lib</code>. Otherwise it is the libdir
    specified when GTK+ was configured, usually
    <code class="filename">/usr/lib</code>, or
    <code class="filename">/usr/local/lib</code>.)
    For each directory in this list, GTK+ actually looks in a
    subdirectory
    <code class="filename"><em class="replaceable"><code>directory</code></em>/<em class="replaceable"><code>version</code></em>/<em class="replaceable"><code>host</code></em>/<em class="replaceable"><code>type</code></em></code>
    Where <em class="replaceable"><code>version</code></em> is derived from the
    version of GTK+ (use <code class="literal">pkg-config
    --variable=gtk_binary_version gtk+-3.0</code> to determine this from a
    script), <em class="replaceable"><code>host</code></em> is the architecture on
    which GTK+ was built. (use <code class="literal">pkg-config
    --variable=gtk_host gtk+-3.0</code> to determine this from a
    script), and <em class="replaceable"><code>type</code></em> is a directory
    specific to the type of modules; currently it can be
    <code class="literal">modules</code>, <code class="literal">engines</code>,
    <code class="literal">immodules</code>, <code class="literal">filesystems</code> or
    <code class="literal">printbackends</code>, corresponding to the types of
    modules mentioned above. Either <em class="replaceable"><code>version</code></em>,
    <em class="replaceable"><code>host</code></em>, or both may be omitted. GTK+ looks
    first in the most specific directory, then in directories with
    fewer components.
    The components of GTK_PATH are separated by the ':' character on
    Linux and Unix, and the ';' character on Windows.
  </p>
<div class="warning">
    Note that this environment variable is read by GTK+ 2.x too, which
    makes it unsuitable for setting it system-wide (or session-wide),
    since doing so will cause either GTK+ 2.x applications or GTK+ 3
    applications to see incompatible modules.
  </div>
<p><b><code class="envar">GTK_IM_MODULE</code>. </b>
    Specifies an IM module to use in preference to the one determined
    from the locale. If this isn't set and you are running on the system
    that enables <code class="literal">XSETTINGS</code> and has a value in
    <code class="literal">Gtk/IMModule</code>, that will be used for the default
    IM module.
    This also can be a colon-separated list of input-methods, which
    GTK+ will try in turn until it finds one available on the system.
  </p>
<p><a name="gtk-im-module-file"></a><b><code class="envar">GTK_IM_MODULE_FILE</code>. </b>
    Specifies the file listing the IM modules to load. This environment
    variable the default value
    <code class="filename"><em class="replaceable"><code>libdir</code></em>/gtk-3.0/3.0.0/immodules.cache</code>
    (<em class="replaceable"><code>libdir</code></em> has the same meaning here as explained for <code class="envar">GTK_PATH</code>).
  
    The <code class="filename">immodules.cache</code> file is generated by the
    <span class="command"><strong>gtk-query-immodules-3.0</strong></span> utility.
  </p>
<div class="warning">
    Note that this environment variable is read by GTK+ 2.x too, which
    makes it unsuitable for setting it system-wide (or session-wide),
    since doing so will cause either GTK+ 2.x applications or GTK+ 3
    applications to see the wrong list of IM modules.
  </div>
<p><b><code class="envar">GTK_EXE_PREFIX</code>. </b>
    If set, GTK+ uses <code class="filename">$GTK_EXE_PREFIX/lib</code> instead of
    the libdir configured when GTK+ was compiled.
  </p>
<p><b><code class="envar">GTK_DATA_PREFIX</code>. </b>
    If set, makes GTK+ use <code class="filename">$GTK_DATA_PREFIX</code>
    instead of the prefix configured when GTK+ was compiled.
  </p>
<p><b><code class="envar">GTK_THEME</code>. </b>
    If set, makes GTK+ use the named theme instead of the theme
    that is specified by the gtk-theme-name setting. This is intended
    mainly for easy debugging of theme issues.
  
    It is also possible to specify a theme variant to load, by appending
    the variant name with a colon, like this: `GTK_THEME=Adwaita:dark`.
  </p>
<p>
The following environment variables are used by GdkPixbuf, GDK or
Pango, not by GTK+ itself, but we list them here for completeness
nevertheless.
</p>
<p><b><code class="envar">GDK_PIXBUF_MODULE_FILE</code>. </b>
    Specifies the file listing the GdkPixbuf loader modules to load.
    This environment variable overrides the default value
    <code class="filename"><em class="replaceable"><code>libdir</code></em>/gtk-3.0/3.0.0/loaders.cache</code>
    (<em class="replaceable"><code>libdir</code></em> is the sysconfdir specified when
    GTK+ was configured, usually <code class="filename">/usr/local/lib</code>.)
  
    The <code class="filename">loaders.cache</code> file is generated by the
    <span class="command"><strong>gdk-pixbuf-query-loaders</strong></span> utility.
  </p>
<p><a name="GDK-Debug-Options"></a><b><code class="envar">GDK_DEBUG</code>. </b>
  If GTK+ has been configured with <code class="option">--enable-debug=yes</code>,
  this variable can be set to a list of debug options, which cause GDK
  to print out different types of debugging information.
  </p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term">cursor</span></p></td>
<td><p>Information about cursor objects (only win32)</p></td>
</tr>
<tr>
<td><p><span class="term">dnd</span></p></td>
<td><p>Information about drag-and-drop</p></td>
</tr>
<tr>
<td><p><span class="term">draw</span></p></td>
<td><p>Information about drawing operations (only win32)</p></td>
</tr>
<tr>
<td><p><span class="term">eventloop</span></p></td>
<td><p>Information about event loop operation (mostly Quartz)</p></td>
</tr>
<tr>
<td><p><span class="term">misc</span></p></td>
<td><p>Miscellaneous information</p></td>
</tr>
<tr>
<td><p><span class="term">nogl</span></p></td>
<td><p>Turn off OpenGL. GDK will behave as if OpenGL support was not available.</p></td>
</tr>
<tr>
<td><p><span class="term">nograbs</span></p></td>
<td><p>Turn off all pointer and keyboard grabs</p></td>
</tr>
<tr>
<td><p><span class="term">xinerama</span></p></td>
<td><p>Simulate a multi-monitor setup</p></td>
</tr>
<tr>
<td><p><span class="term">xim</span></p></td>
<td><p>Information about XIM support</p></td>
</tr>
</tbody>
</table></div>
<p>
  The special value <code class="literal">all</code> can be used to turn on all
  debug options.
  </p>
<p><b><code class="envar">GDK_RENDERING</code>. </b>
    If set, selects the way how GDK creates similar surfaces. This affects both the
    functionality of the function gdk_window_create_similar_surface() as well as the
    way GDK creates backing surfaces for double buffering. The following values can
    be used:
    </p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term">similar</span></p></td>
<td><p>Create similar surfaces to the window in use. This is the
          default behavior when the variable is not set.</p></td>
</tr>
<tr>
<td><p><span class="term">image</span></p></td>
<td><p>Always create image surfaces. This essentially turns off
          all hardware acceleration inside GTK.</p></td>
</tr>
<tr>
<td><p><span class="term">recording</span></p></td>
<td><p>Always create recording surfaces. This causes bare rendering
          to the backend without the creation of intermediate surfaces (Pixmaps in X)
          and will likely cause flicker.</p></td>
</tr>
</tbody>
</table></div>
<p>
    All other values will be ignored and fall back to the default behavior. More
    values might be added in the future. 
  </p>
<p><b><code class="envar">GDK_BACKEND</code>. </b>
    If set, selects the GDK backend to use. Selecting a backend requires that
    GTK+ is compiled with support for that backend. The following backends can
    be selected, provided they are included in the GDK libraries you are using:
    </p>
<div class="variablelist"><table border="0" class="variablelist">
<colgroup>
<col align="left" valign="top">
<col>
</colgroup>
<tbody>
<tr>
<td><p><span class="term">quartz</span></p></td>
<td><p>Selects the native Quartz backend</p></td>
</tr>
<tr>
<td><p><span class="term">win32</span></p></td>
<td><p>Selects the native backend for Microsoft Windows</p></td>
</tr>
<tr>
<td><p><span class="term">x11</span></p></td>
<td><p>Selects the native backend for connecting to X11 servers.</p></td>
</tr>
<tr>
<td><p><span class="term">broadway</span></p></td>
<td><p>Selects the Broadway backend for display in web browsers</p></td>
</tr>
<tr>
<td><p><span class="term">wayland</span></p></td>
<td><p>Selects the Wayland backend for connecting to Wayland display servers</p></td>
</tr>
</tbody>
</table></div>
<p>
    Since 3.10, this environment variable can contain a comma-separated list
    of backend names, which are tried in order. The list may also contain
    a *, which means: try all remaining backends. The special value "help" can
    be used to make GDK print out a list of all available backends.
    For more information about selecting backends, see the gdk_display_manager_get() function.
  </p>
<p><b><code class="envar">GTK_CSD</code>. </b>
    The default value of this environment variable is 1. If changed to 0, this
    disables the default use of client-side decorations on GTK+ windows, thus
    making the window manager responsible for drawing the decorations of
    windows that do not have a custom titlebar widget.
  
    CSD is always used for windows with a custom titlebar widget set, as the WM
    should not draw another titlebar or other decorations around the custom one.
  </p>
<p><b><code class="envar">GTK_OVERLAY_SCROLLING</code>. </b>
    The default value of this environment variable is 1, which means that each
    instance of GtkScrolledWindow will choose whether to use overlay or full-
    size scrollbars via its own GtkScrolledWindow:overlay-scrolling property,
    which defaults to <code class="literal">TRUE</code>. If this variable is set to 0,
    all GtkScrolledWindow instances are made to use full/non-overlay scrollbars.
  </p>
<p><b><code class="envar">XDG_DATA_HOME</code>, <code class="envar">XDG_DATA_DIRS</code>. </b>
    GTK+ uses these environment variables to locate icon themes
    and MIME information. For more information, see
    <a class="ulink" href="https://freedesktop.org/Standards/icon-theme-spec" target="_top">Icon Theme Specification</a>,
    the <a class="ulink" href="https://freedesktop.org/Standards/shared-mime-info-spec" target="_top">Shared MIME-info Database</a>
    and the <a class="ulink" href="https://freedesktop.org/Standards/basedir-spec" target="_top">Base Directory Specification</a>.
  </p>
<p><b><code class="envar">DESKTOP_STARTUP_ID</code>. </b>
    GTK+ uses this environment variable to provide startup notification
    according to the <a class="ulink" href="https://standards.freedesktop.org/startup-notification-spec/startup-notification-latest.txt" target="_top">Startup Notification Spec</a>.
    Following the specification, GTK+ unsets this variable after reading
    it (to keep it from leaking to child processes). So, if you need its
    value for your own purposes, you have to read it before calling
    gtk_init().
  </p>
</div>
<hr>
<div class="refsect2">
<a name="interactive-debugging"></a><h3>Interactive debugging</h3>
<img src="inspector.png"><p>
    GTK+ includes an interactive debugger, called the GTK+ Inspector, which
    lets you explore the widget tree of any GTK+ application at runtime, as
    well as tweak the theme and trigger visual debugging aids. You can
    easily try out changes at runtime before putting them into the code.
  </p>
<p>
    Note that the GTK+ inspector can only show GTK+ internals. It can not
    understand the application-specific logic of a GTK+ application. Also,
    the fact that the GTK+ inspector is running in the application process
    limits what it can do. It is meant as a complement to full-blown debuggers
    and system tracing facilities such as DTrace, not as a replacement.
  </p>
<p>
    To enable the GTK+ inspector, you can use the Control-Shift-I or
    Control-Shift-D keyboard shortcuts, or set the
    <code class="envar">GTK_DEBUG=interactive</code> environment variable.
  </p>
<p>
    In some situations, it may be inappropriate to give users access to the
    GTK+ inspector. The keyboard shortcuts can be disabled with the
    `enable-inspector-keybinding` key in the `org.gtk.Settings.Debug`
    GSettings schema.
  </p>
</div>
</div>
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